5.2 Displacement Reactions

Agenda Lesson 5.2 Displacement Reactions Vocabulary Learning Check page 195 1, 2 Practice Problems page a, b, c page a, b, c

Learning Goals Students will discuss and solve single displacement reactions Students will be introduced to and work with the activity series of elements Students will discuss and solve double displacement reactions

Displacement Reactions Many industrial processes, such as the one used to isolate nickel from the deposits found around Sudbury, rely on a series of chemical reactions that include the displacement of one element by another to form a new compound.

Single Displacement Reactions A single displacement reaction is a chemical reaction in which one element (a reactive metal or non-metal) takes the place of an element in a compound to produce another element and another compound A + BC AC + B Where A is a metal A + BC BA + C Where A is a non-metal

Examples of Single Displacement Reactions Displacing Metals with Metals Producing copper (Cu) metal Mg(s) + CuSO 4 (aq) MgSO 4 (aq) + Cu (s) Replacing Hydrogen with Metals Producing zinc chloride (ZnCl 2 ) and hydrogen gas (H 2 ) Zn(s) + 2HCl(aq) ZnCl 2 (aq) + H 2 (g) Zinc displaces the hydrogen from hydrochloric acid to produce zinc chloride and hydrogen gas. Displacing silver (Ag) from silver nitrate (AgNO 3 ) Copper displaces the silver to produce a blue copper (II) nitrate solution and solid silver deposits. Cu(s) + 2AgNO 3 (aq) Cu(NO 3 ) 2 (aq) + 2Ag(s)

Activity Series The activity series is a list of elements organized according to their chemical reactivity. The most reactive element appears on the top, and the least reactive appears at the bottom. Remember! Metals can only replace other metals in a reaction, and non- metals can only replace other non- metals. Metals higher up on the activity series list will replace metals lower on the list during a single displacement reaction.

Sample Problem: Predicting Products of a Single Displacement Reaction for Metals.

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Replacing Non-Metal Ions The ion of a non-metal such as the chloride ion is negatively charged, so it can be replaced only with another non-metal. There is a separate activity series for non-metals. It works the same way as the activity series for metals, with the most reactive element at the top of the list. Non-metals F Most reactive Cl Br I Least reactive

Double Displacement Reactions A double displacement reaction is a chemical reaction in which the positive ions of two different compounds exchange places, resulting in the formation of two new compounds – one of which may be a precipitate. A and C are cations (+) and B and D are anions (-)

When a colourless aqueous solution of silver nitrite is added to a yellow aqueous solution of potassium chromate, silver chromate (AgCrO 4 (s) ) (the red precipitate) and potassium nitrate (2KNO 3 (aq)) are formed.

Sample Problem: Predicting Products of Double Displacement Reactions

Chemical Reactions and Food Preservation Sulfur dioxide (SO 2 ) is used to preserve the colour of dried fruit. A double displacement reaction followed by a decomposition reaction releases the sulfur dioxide gas required for the process. The sulfur dioxide is absorbed into the skin of the fruit and prevents is from darkening and changing flavour as it dries. The double replacement reaction Na 2 SO 3 (aq) + 2HCl(aq) 2NaCl (aq) + H 2 SO 3 (aq) The decomposition reaction H 2 SO 3 (aq) H 2 O(l) + SO 2 (g)

Summary of Reaction Types

One additional type of chemical reaction that you will learn about in future studies is a combustion reaction. These reactions always involve a “fuel” reacting with oxygen to release energy. Carbon dioxide and water are also produced by the reaction.

Success Criteria I am able to discuss and solve single displacement reactions I am able to understand the activity series of elements I am able to double displacement reactions and solve double displacement reactions